Talk:Cosmic microwave background

Addition of Explanation of the impact the temperature of the CMB's quantum fluctuations has on the Density of matter in the Universe

The article should include an explanation of how high temperatures after the Big Bang due to quantum fluctuations resulted in higher mass densities of localities throughout the Universe. Something explaining that warmer areas are denser and cooler areas are more void-like would be good to include. ScientistBuilder (talk) 19:21, 12 October 2021 (UTC)ScientistBuilderScientistBuilder (talk) 19:21, 12 October 2021 (UTC)

It's actually the other way around! Areas where the CMB temperature is higher are less dense, and areas where the CMB temperature is lower are more dense. [1], [2] --Amble (talk) 19:10, 22 October 2021 (UTC)

This topic is briefly mentioned in the Multipole section but could be expanded upon. Praemonitus (talk) 19:25, 22 October 2021 (UTC)

Regarding the correspondence between temperature and overdensities, it is actually a scale dependent phenomenon. As the user above points out, at large scales (l<100 ish) overdensities correspond to cool spots due to the integrated Sachs Wolfe effect, and vice versa for underdensities. However, at small scales the anisotropies are generated by acoustic physics in the primordial plasma. There, compression during baryon-acoustic oscillations heats up the plasma and overdensities can correspond to hot spots. Fireballs619 (talk) 04:09, 28 January 2024 (UTC)

Article issues and classification

The "Primary anisotropy" subsection has three unsourced paragraphs. The "Adiabatic density perturbations" section is unsourced. All but one sentence of the "Isocurvature density perturbations" subsection is unsourced and has a "citation needed" tag. The "Late time anisotropy" is unsourced with "clarification needed" tags. Other paragraphs are also unsourced.

The B-class criteria #1 states; The article is suitably referenced, with inline citations. It has reliable sources, and any important or controversial material which is likely to be challenged is cited. At present the article does not meet the criteria for B-class assessment. -- Otr500 (talk) 03:15, 28 February 2023 (UTC)

I'm not sure it fully satisfies criteria 6 either: "The article presents its content in an appropriately understandable way". In particular, the "Data reduction and analysis" section may not be useful to a lay reader. It's probably at a B− rating, rather than a C rating. Praemonitus (talk) 04:26, 28 February 2023 (UTC)

Polarization section reorg.

The "Polarization" section had at least four copies of the same material mixed around. I've edit it down to two duplicates now.

The B-mode polarization is contaminated by E-mode polarization seen through gravitational lensing. This is per Hanson et al. and I believe this is the way astrophysics looks at B-mode. So I changed the text from discussion of two types of B-mode to a more layered 1-2 form.

The last two subsections of the Polarization section again repeat the same material with more (primary) references and details. These section should be merged with B-mode above it or possibly made sub-subsections of B-mode. Johnjbarton (talk) 18:33, 8 May 2024 (UTC)

This Annual Review is exceptionally clear and comprehensive:

• Kamionkowski, Marc, and Ely D. Kovetz. "The quest for B modes from inflationary gravitational waves." Annual Review of Astronomy and Astrophysics 54 (2016): 227-269.

Johnjbarton (talk) 18:05, 10 May 2024 (UTC)

Redundant, repetitious material that repeats in different places.

The article has roughly the same material in different places. Needs to be cleaned up. Thus my reorganization and deletion edits. Johnjbarton (talk) 18:38, 10 May 2024 (UTC)